In the 40 years since Monsanto first commercialized glyphosate, the pesticide giant has encouraged growers to liberally douse their fields in the product best known by the brand name Roundup — the more, the better.

After all, the pesticide maker assured users, glyphosate is “safer than table salt” and weeds would likely never develop resistance to it.

Neither of those assertions was true. But annual U.S. glyphosate use soared to more than 300 million pounds, including 10 million pounds used just in California. Not surprisingly researchers are now detecting traces of the pesticide in a wide range of off-the-shelf foods, including many California wines — even organic brands.

And that creates an uncomfortable problem for the pesticide maker and its customers as the state of California pushes toward listing glyphosate as a known human carcinogen under Proposition 65. That could happen any day now in the wake of Friday’s final court decision rejecting Monsanto’s latest challenge.

In the two years since regulators announced their intent to list glyphosate, Monsanto has done its best to sow doubt in the finding that triggered the decision — the conclusion by the World Health Organization that the best scientific research indicates glyphosate is a “probable” carcinogen in humans.

But it’s a tough task, even for Monsanto, to cast doubt on findings of the WHO’s International Agency for Research on Cancer, considered the gold standard for cancer research. In 50 years, not a single “probable” human carcinogen it has identified has been shown later to not cause cancer.

Unable to undermine the research, Monsanto pushed forward with the legal argument recently rejected by the courts — that it is unlawful to have an unelected, foreign body like the WHO inform the state’s policies, as if the world’s best scientific research should be ignored.

The California EPA would be the first U.S. regulatory body to recognize the most widely used pesticide in the world, as well as in the U.S. and California, as a carcinogen.

Just here in California, 2 million more pounds of the pesticide are now applied each year than in 2010, and use has more than doubled since 2000.

The risks of using of glyphosate are not evenly spread across socio-economic lines. An analysis I completed last year found that more than half of the glyphosate sprayed in California was applied in the eight most impoverished counties, which are predominantly Latino.

Monsanto argues that the increase in glyphosate use is good because the company’s flagship pesticide has displaced other more-toxic herbicides. But its overuse has directly fueled the escalating resistance in weeds, which has spurred many growers to once again start using the older herbicides in addition to glyphosate.

The towering glyphosate-resistant superweeds now commonplace across 100 million U.S. acres are typically associated with Midwestern commodity crops genetically engineered to resist the pesticide. But glyphosate resistance is also a growing problem in California.

With six different species of glyphosate resistant weeds now identified in California, growers here are being urged by Monsanto to apply both glyphosate and some of the older, more-toxic herbicides at the same time.

It’s even becoming common practice to mix pesticides to delay the inevitable development of resistance. So some pesticides are now being used on our food not to combat pests but to help maintain the efficacy of other pesticides.

As a result, growers are now paying for more pesticides while American families and wildlife are being exposed to an ever more complex mixture of poisons.

Instead of solving America’s weed problem, America’s deepening addiction to glyphosate has put us on a treadmill that can only lead to greater pesticide use.

And that addiction may put some of us at greater risk of developing cancer.

Nathan Donley is a senior scientist in the Center for Biological Diversity’s environmental health program. He wrote this for The Mercury News.